The global expansion of coastal cities could leave more than three quarters of their neighbouring seafloor exposed to potentially harmful levels of light pollution.
A study led by the University of Plymouth (UK) showed that under both cloudy and clear skies, quantities of light used in everyday street lighting permeated all areas of the water column.
This could pose a significant threat to coastal species, with recent research also involving the University showing that the presence of artificial skyglow can disrupt the lunar compass that species use when covering long distances.
However, the current study found that the colour of the wavelengths shone at the surface had a marked effect on how much biologically important light pollution reached the seafloor.
Many of the white LEDs now being used to illuminate the world’s towns and cities use a mixture of green, blue and red wavelengths to generate their brightness.
Green and blue wavelengths left up to 76% and 70% of the three-dimensional seafloor area exposed to light pollution, respectively, while the presence of red light was less than 1%.
The research – which also involved Bangor University, the University of Strathclyde and Plymouth Marine Laboratory – is published in Scientific Reports, an online journal from the publishers of Nature.
It is the first study in the world to quantify the extent to which biologically important artificial light is prevalent on the seafloor and could, in turn, be having a detrimental effect on marine species.
Dr Thomas Davies, Lecturer in Marine Conservation at the University of Plymouth and the paper’s lead author, made the following statement: